Temperature-independent oscillatory circuits



Nov. l, 1938. H1 MUTH ET AL 2,134,794

TEMPERATURE INDEPENDENT OSGILLATORY CIRCUITS Filed April 19, 1934 HERBERT MUTH BYWILHI/T' RUNGE A'T ORNEY Patented Nov. l, 1,938 I n UNITED `STATES PATENT ori-ics TEMPERATURE-INDEPENDENT OSCILLA- Y TORY CIRCUITS y Application April 19, 1934. serial No. 'izmir In Germany April lil, 1933 1 Claim. (Cl. Z50-40) The present invention relates to means and apparatus for rendering tuned circuits and like parts of radio transmitting and receiving apparatus and wave meters independent of tem- 5 perature changes. l l

High frequency oscillatory circuits whose natural frequency, is rendered independent of temperature changes by suitable means are `known in the art.

l devices has heretofore been restricted to transmitters. With the growing use of ultra-short waves, receivers-and wave meters must meet particularly high requirements as to selectivity. Hence, in such cases it often becomes necessary l to utilize temperature independent circuits.`

It is an object of the present invention to devise temperature independent circuits adaptable for use in the devices mentioned above.

In accordance with the invention, reactance elements, for instance, condensers and chokes may be rendered independent of temperature iiuctuations as regards the capacity or inductance respectively of the elements, by using as current conducting parts, metal layers upon carriers of ceramic materials possessing an extremely small heat expansion coefficient. Asa rule, Ain such condensers or chokes the ceramic supports for the metal layers are `the only parts of the structure formed of material having a small coeiiicient of expansion. In general, additional members must be provided for the assemblage of the single insulating parts, for the control of variable reactances, and as by-pass means etc.

v In accordance with another feature of the invention, such parts are made of metal alloys of a very small heatexpansion coeflicient, preferably of nickel-steel alloys known by the designation .Invar or of similar alloys, mainly containing nickel and steel.

40 Still another feature of the invention relates to a suitable mechanical assemblage of the reactance elements of an oscillatory circuit so that it is independent oirtemperature changes. It is often necessary, to combine the constituents of the oscillatory circuit, i. e., the chokes and condensers, as closely as possible, in order to use short leads. The invention is based upon the recognized fact that in such a case it is not immaterial in what manner. the single reactances of 5o the circuit are arranged with respect to each other. If, for instance, the common mechanical `support of two reactance elements has a considerableheat expansion coeillcient, it may happen that the distance between the single .reactance elements which varies on account of the However, the use of such expansion of the carrier, due to heat, may change the self inductance or the value of the'capacity thereof to such an extent as to cause a notable change i'n the frequency.

In accordance with the invention, materials 5 having a practically negligible heat expansion coefliclent, are used for the mechanical assemblage of single reactance units of oscillatory circuits which are independent in regard to heat.

If a member mechanically connecting the-two Al0 units is also used as an electrical connection, it is suitably formed of a metal alloy possessing a practically negligible heat expansion coefficient. Such alloys are known in the art by various terms such as Invar, Indilatan etc., and contain as an ll essential if not singl'e constituent a nickel-steel alloy. However, it is also possible to use for mechanically assembling single reactance umts, supports of ceramic material likewise of negligibly small heat expansion coeilicient. case, the electrical connections can be applied to these supports in the form of metallic layers of suitable width, or they may be connected to the support in another manner so that they will not be deformed by the action of heat. 25

Certain features `of the invention are illustrated in the accompanying drawing in which Fig. 1 illustrates the application to a single reactor, as, for instance, a condenser; and Figure 2 illustrates the application of a feature of the 30 invention'to a tuned circuit.

In Figure 1 a and b are supports of ceramic material for the metal layers c and d respective- 1y. The supports a and b are of an approximate cup shape. A control axis e composed of nickel 35 steel alloy of constant temperature coeflicient, for instance Invar, is provided with a. screw thread f, having a sleeve a movably arranged thereon. The sleeve g consists of similar material and carries the condenser part b. In tum- 40 ing the shaft e thereby axially displacing the two ycylinders with respect to each other, the capacity can be changed in a manner known per se. In forming the parts e and a of a suitable nickelsteel alloy,v a feature not required as such with 45 vregard to electrical considerations (these parts In this 20 A coil i hss its current conducting winding likewise-applied as s layer to s. oersmic body i.

rn m. 2 the :wo clustery cli-ems simu h,

and i are connected together by means o! the members l, k which are made o! s metal hlvinl' a. negligibly small heat expansion coetcient, ss. yfor instance, the metal alloy known ss Invsr. In this case, one end oi the member l is connected to the metallic layer of the condenser h at the point 6 while the other end is connected to.

'. embersbeinl physically connected to said supports for msmtsiningthesupportsinproperspscerelstionship withrespecttoeschother.

HERBERT MUTE. vWILHELM RUNGI. 

